We propose an R01 study by a new, early stage investigator that seeks to understand and improve naloxone implementation within syringe service programs (SSPs) to reduce opioid overdose mortality in the United States. The age-adjusted opioid overdose mortality rate rose nearly 200% from 2000 to 2014 and increased another 16% from 2014 to 2015. These data indicate that the opioid overdose epidemic continues to surge in the United States. Naloxone is an evidence-based biomedical intervention that reverses opioid overdose, effectively preventing opioid overdose mortality. The study team has developed an implementation manual for naloxone implementation in various settings including SSPs. Yet, only 15% of U.S. counties with the highest overdose mortality levels have a community-based, naloxone program operating within them. Furthermore, only 56% of SSPs, one of the best venues through which to implement this intervention, have implemented naloxone. A nuanced understanding of where naloxone delivery within SSPs falls along the four phases of the implementation process?from Exploration and Preparation to Implementation and Sustainment (EPIS)?is critical to focus intervention efforts. A recent systematic review concluded that dissemination alone is necessary but often insufficient to advance the desired adoption of interventions. There is, therefore, an urgent need to empirically identify implementation strategies that can significantly improve upon dissemination approaches. One such strategy?external facilitation?has demonstrated effectiveness in medical settings, but no research has experimentally tested its use to improve delivery of a biomedical intervention in community- based organizations such as SSPs. We propose an external facilitation intervention, shown to improve implementation in HIV service settings, to identify barriers to and needs for and facilitate start-up of naloxone delivery within SSPs. Aim 1 is to characterize U.S. SSPs along the exploration, preparation, implementation, and sustainment continuum for delivering the naloxone intervention. Aim 2 is to test the effectiveness of external facilitation to improve the advancement of the naloxone intervention along the EPIS continuum among U.S. SSPs compared with dissemination of the implementation manual alone. To achieve Aim 1, we will conduct a cross-sectional study with all SSPs (N=275) throughout the United States. To achieve Aim 2, we will conduct a randomized controlled trial with the following arms: (1) dissemination of an implementation manual and external facilitation for 12 months (experimental arm) and (2) dissemination of an implementation manual only (control arm). All SSPs not yet implementing naloxone and interested in participating (estimated N = 100) will be randomly assigned in a 1:1 ratio to the study arms. Advancement of naloxone along the EPIS continuum will be assessed via surveys 12 months post randomization. Together, these efforts can improve access to naloxone for people at high risk of overdose, thereby improving our nation's response to the opioid overdose epidemic.